Although hard to go wrong at the price for anything that runs, better check it out carefully to make sure that's all it needs. On a 25 year old car anything goes and it's not worth putting a lot of money into something like that.

new radiator $300

new exhaust system $700

Now your quarter century, high mileage car costs almost $2k.

He "says" it's leaking from the radiator and has an exhaust leak.  Maybe it's really leaking from a blown head gasket and the exhaust manifold is cracked.  Do you actually know? Pay attention to what @mmj said.  And that's just the cost for the parts, not the labor.

Since you say you can do the work yourself, research all the parts needed to fix them and then you can make a better decision if it's worth it. Used sleds are always a gamble... Do you feel lucky?

You don't want somebody else's beater car. If they didn't take care of their cooling system who knows what else they didn't take care of. On the other hand if the rest of the car seems mint, than maybe that's a decent deal.